1. Field of the Invention
The present invention concerns the molding of articles such as hollow glassware. More particularly, it concerns a new glass making machine capable of executing a wide range of articles.
2. Description of the Prior Art
Glass pressing machines used in making hollow glassware permit execution of a generally narrow range of molded articles. Thus, there are distinguishable pressing machines for small articles, for example articles of about 40 to 150 mm in diameter, pressing machines for medium-sized articles, for example articles of about 150 to 260 mm in diameter, and machines adapted to the production of large articles, for example articles exceeding 260 mm in size.
For producing small or medium-sized articles, pressing machines have one or a plurality (generally two) of pressing devices with an equal number of dies. The devices are pneumatically controlled by simultaneous operation to permit a relatively high rate of production. For example, a pressing machine having double pressing devices can produce on the order of 60-50-mm tumblers per minute.
Known pneumatically controlled machines display a number of disadvantages. In addition to their specialization and their limitation to a given and relatively narrow range of articles, they have a major drawback, due essentially to their pneumatic control. Such control mechanisms permit no control over the travel of the die or dies attached at the ends of the rams of the pressing devices. Thus, the impact of the dies with the mass of glass to be formed, called the parison, approaches hammering. This results in defects in appearance of the molded article such as distortion, folds, etc.
For producing larger articles, for example about 300 mm in diameter, the pressing machines used may have either pneumatic or hydraulic control devices. Where the control mechanism is pneumatic, the pressing machine is equipped with a toggle mechanism, i.e., a device making it possible to increase the pressure of the die during formation of the article. In addition to the above-mentioned drawbacks inherent in the single pneumatic control, such toggle machines have the disadvantage of requiring a very bulky pressing device due to the presence of the toggle mechanism. This is the reason why these machines generally include only one pressing device.
Where, as an alternative, the die in the pressing machine is hydraulically controlled, a greater stamping force is imparted to the die than can be with a pneumatic operation. This permits elimination of the toggle mechanism. To the gain in space obtained by getting rid of the toggle mechanism are added other advantages, such as the possibility of controlling the speed of stamping during formation of the article in the mold, less noisy stamping, etc. A machine with a hydraulic control of this type is described in U.S. Pat. No. 3,953,187. The articles produced by these hydraulic pressing machines are generally of good quality. The essential disadvantage of these machines, in general, is the slow rate of production of articles.